In-use testing with Portable Emissions Measurement Systems (PEMS) has received attention by policy makers and industry as an effective and cost-efficient means to verify emissions of a wide range of vehicles. We provide an overview of the state-of-the-art PEMS in-use emissions testing in the current and future European emissions legislation for light-duty and heavy-duty vehicles as well as non-road mobile machinery.For obtaining type approval in European Union (EU), light-duty vehicles have to comply with Euro 6 emission standards from January 2014 onward. In parallel, a new test procedure will complement standard emissions testing in the laboratory to control gaseous and particulate emissions over a wide range of real-world driving conditions. Two candidate procedures are developed at present, i.e., random cycle testing and on-road emissions testing with PEMS. Currently, key challenges are the definition of test conditions and design of a suitable method for data evaluation.For heavy-duty vehicles, in-use testing with PEMS is already enforced in the European Union since 2009. The revision of European requirements will be completed in 2014 and shifts the focus from engine conformity checking towards the assessment of emissions under real-world driving conditions. The feasibility of PEMS for measuring particle mass is currently investigated by an industry-run pilot program. Moreover, the application of PEMS to Stage IV and V engines of non-road mobile machinery is currently under discussion.We conclude that in-use testing with PEMS will play an important role in the future European vehicle emissions legislation. The application of PEMS can effectively control vehicle emissions, may accelerate the adoption of novel emission abatement technologies and thereby contribute to air quality improvements throughout Europe.